1. Field of the Invention
The present invention relates to a link mechanism of a reciprocating internal combustion engine.
2. Description of the Related Art
A conventional link mechanism of an internal combustion engine has a piston making a reciprocating motion which is transmitted to a crank shaft via a plurality of link members, thus rotating the crank shaft.
As is seen in FIG. 8 and FIG. 9, Japanese Patent Unexamined Publication No. Heisei 9 (1997)-228858 (=JP9228858) discloses the link mechanism of the internal combustion engine.
A lower link 42 is rotatably supported to a crank pin 41 of a crank shaft 40. Lower link 42 has a first end (left in FIG. 8) connected to a lower end of an upper link 44 via an upper pin 43. Lower link 42 has a second end (right in FIG. 8) connected to a lower end of a control link 46 via a control pin 45.
Upper link 44 has an upper end connected to a piston 48 via a piston pin 47. Control link 46 has an upper end connected to a control shaft 49 supported with a body of the internal combustion engine.
In the above construction, lower link 42 is swingably controlled (restricted) with control link 46 via control pin 45.
A predetermined line E′ extends through a center C′ of a crank main shaft 50 substantially in parallel with a direction along a reciprocating motion of piston 48. Moreover, an axial line G′ (track G′) of a center F′ of piston pin 47 and a track I′ of a center H′ of upper pin 43 are tracked in accordance with the reciprocating motion of piston 48.                With respect to predetermined line E′, control shaft 49 is disposed on a right side, as is seen in FIG. 8 and FIG. 9.        With respect to predetermined line E′, axial line G′and track I′are disposed on a leftside, as is seen in FIG. 8. and FIG. 9.        
A swingable center A′ of control link 46 is disposed upper than center C′ of crank main shaft 50 in the direction along the reciprocating motion of piston 48.
There is provided a track K′ of a center J′ of control pin 45. Track K′ is movable in accordance with the reciprocating motion of piston 48. As is seen in FIG. 9, track K′ is shaped substantially into an arc protruding downward in the direction substantially along the reciprocating motion of piston 48.